Pearls for Arterial Blood Pressure Monitoring1. Blood pressure is only one data point for patient assessment.
2. The blood pressure number is accurate only if you have a reliable waveform.
3. In the situation where the non-invasive blood pressure (cuff) is different than the arterial blood pressure, consult with your ICU team to establish the blood pressure number to trend.
Arterial Blood Pressure Fundamentals
In critically ill patients, an arterial line (artline) is often placed to more accurately measure arterial pressure1-2. Artline catheters are usually placed in either a radial artery in the wrist, or a femoral artery in the groin. These catheters directly sample the patient’s arterial pressure.
An arterial line set-up consists of a pressure bag, a 500ml bag of NS or Heparinized NS (depending on your facility guidelines), a transducer kit (similar to IV tubing, but has transducing chip in line and a cord to connect to transducer cable), a transducer cable that connects to monitor, and a holder for the transducer.
You will see that this transducer set-up has a syringe in line. Not all transducer set-ups have a syringe in line.
You will notice the demonstrator changing the cap on the line after zeroing it. This is very important. Different set-ups will have different numbers of caps. The important thing to remember is that all caps that were on the line when it comes out of the bag should be changed to the additional caps (of different color) that came with the kit.
He also mentions ‘leveling’ the transducer. This is placing the transducer at the level of the patient’s heart. This, combined with zeroing the transducer, eliminates any effect of atmospheric pressure on the transducer. This means that the numbers you see on your screen are a true representation of your patient’s arterial pressure.
Arterial Line Pleths
1. Lehman, Li-wei H et al. “Methods of blood pressure measurement in the ICU.” Critical care medicine vol. 41,1 (2013): 34-40. doi:10.1097/CCM.0b013e318265ea46
2. Muntner, Paul, et al. “Measurement of Blood Pressure in Humans: A Scientific Statement From the American Heart Association.” Hypertension, vol. 73, no. 5, 2019, doi:10.1161/hyp.0000000000000087